1. Field of the Invention
The present invention relates to a structure of a power module and, more particularly, to a structure of a power module including an insulative substrate on which power semiconductor devices (referred to hereinafter as xe2x80x9cpower devicesxe2x80x9d) are mounted and a control circuit substrate on which IC chips for controlling the power devices are mounted.
2. Description of the Background Art
FIG. 14 is a cross-sectional view of a structure of a background art power module. As illustrated in FIG. 14, the background art power module comprises an insulative substrate 104, a control circuit substrate 112, interconnection terminals, leads, or terminal members (although the term xe2x80x9cterminalsxe2x80x9d are used hereinafter) 110, and a case 109. The insulative substrate 104 includes a ceramic plate 101 and metal plates 102, 103. A plurality of power devices 106 are mounted on the metal plate 102 with solder 105. The plurality of power devices 106 are electrically connected to each other through aluminum wires 111. The metal plate 103 is in contact with a base plate 108, with solder 107 therebetween.
A plurality of semiconductor devices 113 for controlling the power devices 106 are mounted on the control circuit substrate 112. An external connection terminal 137 electrically connected to the semiconductor devices 113 are soldered to the control circuit substrate 112.
Each of the interconnection terminals 110 has a first end electrically connected to the metal plate 102 or the power devices 106 through the aluminum wires 111, and a second end connected to the control circuit substrate 112.
The insulative substrate 104, the control circuit substrate 112 and the interconnection terminals 110 are disposed in the case 109. A lower interior space of the case 109 below the control circuit substrate 112 is filled with silicone gel 114. A cover 115 is mounted on top of the case 109. Main electrodes 135 are provided on an upper surface of the case 109 and electrically connected to the power devices 106 through terminals 136 and aluminum wires.
FIG. 15 is an enlarged cross-sectional view of a connection between the second end of one of the interconnection terminals 110 and the control circuit substrate 112. The control circuit substrate 112 has a through hole 118 around which is provided a terminal 116 electrically connected to the semiconductor devices 113. The second end of the interconnection terminal 110 is inserted into the through hole 118 and mounted therein by solder 117 applied around the through hole 118. This provides physical and electrical connections between the second end of the interconnection terminal 110 and the control circuit substrate 112.
However, such a background art power module in which the second end of the interconnection terminal 110 and the control circuit substrate 112 are joined to each other by the solder 117 requires a large number of assembling steps, resulting in increased costs. Additionally, the background art power module is uneconomical since, if a failure occurs in only one of the control circuit substrate 112 and the insulative substrate 104, both of the substrates 112 and 104 must be discarded.
According to a first aspect of the present invention, a power module comprises: a first substrate including a power device; a second substrate opposed to the first substrate and including a semiconductor device for controlling the power device; an interconnection terminal having a first end electrically connected to the first substrate, and a second end electrically connected to the second substrate; and a case having an interior space in which the first substrate, the second substrate and the interconnection terminal are disposed, wherein the second substrate further includes a connector electrically connected to the semiconductor device, and wherein the second end of the interconnection terminal is removably connected to the connector.
Preferably, according to a second aspect of the present invention, in the power module of the first aspect, the connector is disposed near an outer periphery of the second substrate.
Preferably, according to a third aspect of the present invention, in the power module of the first or second aspect, the connector is formed on a main surface of the second substrate which is on the same side as is the semiconductor device.
Preferably, according to a fourth aspect of the present invention, in the power module of any one of the first to third aspects, the connector is formed on a main surface of the second substrate which is opposed to the first substrate.
According to a fifth aspect of the present invention, a power module comprises: a first substrate including a power device; a second substrate opposed to the first substrate and including a semiconductor device for controlling the power device; an interconnection terminal having a first end electrically connected to the first substrate, and a second end electrically connected to the second substrate; and a case having an interior space in which the first substrate, the second substrate and the interconnection terminal are disposed, wherein the second end of the interconnection terminal has elasticity, and wherein the second substrate further includes a conductor pattern formed on a main surface of the second substrate which is opposed to the first substrate, the conductor pattern being electrically connected to the semiconductor device and contacting the second end of the interconnection terminal. The power module further comprises fastening means for removably fixing the case and the second substrate to each other, with the second end of the interconnection terminal displaced upon being pressed by the conductor pattern.
Preferably, according to a sixth aspect of the present invention, in the power module of the fifth aspect, the case includes a receiving surface for placing the second substrate thereon, and the fastening means includes: a first threaded hole formed in the receiving surface; a second threaded hole formed in the second substrate in a position corresponding to the first threaded hole; and a screw configured to be screwed into the first and second threaded holes.
According to a seventh aspect of the present invention, a power module comprises: a first substrate including a power device; a second substrate opposed to the first substrate and including a semiconductor device for controlling the power device; an interconnection terminal having a first end electrically connected to the first substrate, and a second end electrically connected to the second substrate; and a case having an interior space in which the first substrate, the second substrate and the interconnection terminal are disposed, wherein the second substrate further includes a through hole electrically connected to the semiconductor device, and wherein the second end of the interconnection terminal has elasticity in a widthwise direction thereof, and is removably fitted in the through hole.
Preferably, according to an eighth aspect of the present invention, in the power module of any one of the first to fourth and seventh aspects, the case includes a positioning structure for defining a mounting position of the second substrate in the case.
Preferably, according to a ninth aspect of the present invention, in the power module of any one of the first to eighth aspects, at least a connection between the second substrate and the interconnection terminal is sealed with resin.
In accordance with the first aspect of the present invention, the power module is provided in which the second substrate is easy to mount and remove since the second end of the interconnection terminal is removably connected to the connector.
In accordance with the second aspect of the present invention, the second substrate is easily mounted to the second end of the interconnection terminal. Additionally, the amount of flexure of the second substrate is reduced, with the second substrate mounted to the second end of the interconnection terminal. Consequently, an inexpensive material may be used to construct the second substrate, accomplishing reduction in manufacturing costs.
In accordance with the third aspect of the present invention, the power module is reduced in thickness, as compared with a power module including a connector and a second substrate which are formed on different main surfaces.
In accordance with the fourth aspect of the present invention, stresses acting to separate the connector and the second substrate from each other are not exerted, with the second end of the interconnection terminal connected to the connector. Therefore, the connector is prevented from being removed from the second substrate.
In accordance with the fifth aspect of the present invention, the conductor pattern is formed on the main surface of the second substrate which is opposed to the first substrate. Therefore, the power module is reduced in thickness, as compared with a power module including a connector.
In accordance with the sixth aspect of the present invention, the power module is provided in which the second substrate is easy to mount and remove since the case and the second substrate are joined to each other by the screw screwed into the first and second threaded holes.
In accordance with the seventh aspect of the present invention, the power module which is easy to mount and remove is provided since the interconnection terminal and the second substrate are fixed to each other without using solder.
In accordance with the eighth aspect of the present invention, the accuracy of a mounting position of the second substrate in the case is increased.
In accordance with the ninth aspect of the present invention, the resin seal increases the strength of the connection between the second substrate and the interconnection terminal.
It is therefore an object of the present invention to provide a power module which uses no solder to fix an interconnection terminal and a control circuit substrate to each other, facilitating the mounting and removal of the control circuit substrate.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.